Staying ahead of the diesel game

Hydrotreater revamp puts TAIF refinery ahead of diesel regulations

When new diesel quality specifications were on the horizon in Russia, the TAIF-NK refinery in Nizhnekamsk, Tatarstan, needed to find a way to adapt its operations cost-effectively to produce ultra-low-sulphur diesel. “We were driven by the need to produce low-sulphur diesel to meet forthcoming environmental legislation and by the economic benefits of improving the quality of the fuel,” says Rashit Shamgunov, General Manager, TAIF-NK. “Taxes on poorer quality diesel were increasing, while those for the higher-quality, lower sulphur product were falling.”

The Russian government was also gearing up to including domestic heating oil on its list of excisable goods, which enhanced TAIF’s desire to eliminate the fuel from its production line-up and to replace it with ultra-low-sulphur diesel.

The original hydrotreater contained Criterion Catalysts & Technologies (Criterion) catalysts. The strong performance of these catalysts led TAIF refinery to approach Shell Global Solutions, which is affiliated with Criterion, for the revamp of the hydrotreater.

“We had a very positive experience with Criterion and were impressed with the performance of its catalysts. These were still performing to their original specification almost 10 years after being installed, despite only having had a guaranteed cycle length of three years,” says Anatoly Chekashov, Head of the Development Department, TAIF-NK.

Edmundo van Doesburg, Lead Process Engineer, Shell Global Solutions, who was heavily involved in the revamp project, explains, “We were asked to undertake a feasibility study to determine the best option for upgrading the hydrotreater while TAIF conducted a cost assessment. Following this work, TAIF decided to continue with the project, so the hydrotreater was relicensed to Shell Global Solutions on the basis of its revamp design.”

Van Doesburg continues, “As part of the revamp project, we also addressed aspects such as the hydraulic constraints and corrosion problems. TAIF’s desire to co-process visbreaker naphtha was a complicating factor and required an extensive revamp of the work-up section to maximise the diesel yield while meeting the flashpoint specification without defaulting to a costly, energy-intensive atmospheric fractionator.”

Utilising as much of the existing equipment as possible and ensuring that any work would fit in with the normal operations of the refinery were key considerations for the revamp project. “We needed to keep investment costs down and to tie the upgrade into the operation of the refinery to prevent having to shutdown the hydrotreater and lose valuable production time,” Chekashov explains.

Consequently, the work was split into two phases so that it could be carried out during the scheduled 20-day shutdowns of the hydrotreater or while it was still operating. The first stage of the revamp involved installing a new hydrogenation reactor to achieve deeper desulphurisation, new Shell reactor internals, a vacuum stripping column to remove any remaining moisture from the product and new heat exchangers to reduce the thermal input of the unit. This phase of the project was commissioned in June 2012.

The project’s delivery timescale was of utmost importance for TAIF, as the environmental conditions, such as weather constraints, had the potential to affect the project development severely. Therefore, the detailed engineering started before the issue of the final basic engineering package, which consequently required adjustments to the standard project schedule.

“A 300-t reactor was ordered that could only be delivered by sea, which put time pressure on the delivery schedule owing to the risk of the river freezing over during the winter months. It was vitally important that the reactor was on-site before the winter, otherwise, the project would have been held up until the following spring,” explains Chekashov.

Following the first phase, the team achieved a 30% increase in the unit’s capacity to reach 2.015 Mt/y of feedstock. The sulphur content of the diesel produced met the Euro 5 specification of less than 10 ppm.

The second stage renovation kicked off in 2013. This was geared towards making the unit capable of processing all the middle distillates from the refinery and excluding domestic heating oil from the product range. The feedstock pumps at the unit boundary and the pumps for supplying feedstock from the tank farm were replaced. Additional recuperative heat exchangers were included in the circuit and the vacuum splitter column condenser and filtering elements were replaced in the feedstock stream.

This phase of the work lifted the unit’s capacity by almost 50% to 2.3 Mt/y while maintaining the same natural gas and steam consumption for the unit. Despite the increased capacity and significant improvement of the fractionation sharpness between the diesel and the naphtha, the overall thermal energy consumption has not increased owing to the improved heat integration.

A strong working relationship between TAIF and Shell Global Solutions, with constant sharing of ideas and plans, was a key factor in delivering these results.

“This was a challenging project that required a lot of internal planning from the refinery with a strong focus on safety,” says Bogomazov. “Working together as one team meant that we were able to take a flexible and creative approach to the revamp to overcome space and time constraints.”

Finding ways to keep or improve existing pieces of equipment wherever possible also required special planning. TAIF wanted to utilise its existing furnace, so Shell Global Solutions devised a plan to keep it in operation and improve the heat recovery. “As a result of some minor changes to the flow scheme of the heat exchanger, we can now use the heat for other units around the refinery,” says Chekashov.

“The level of expertise of Shell Global Solutions’ technical specialists was tremendous and we were very impressed with their creativity and advice. For instance, they introduced some interesting ideas, including a furnace bypass, a recycle gas circulating reflux cooler and a vacuum splitter column. When they discussed these ideas with our technical experts, the results were fantastic. That strong working relationship is ongoing,” he concludes.

“Many of Shell Global Solutions’ suggestions to alleviate the hydraulic constraints, improve heat integration and enhance the fractionation between the naphtha and the diesel products were implemented and have proven very effective and economically stable, for which we are very grateful. Without these creative ideas, we might not have had such a great result,” adds Bogomazov.

The approximately $50-million revamp project resulted in an overall increase in diesel fuel production of more than 50% between 2011 and 2014. “Everything that Shell Global Solutions and Criterion promised is now a reality,” Shamgunov concludes. “We were able to begin production of Euro 5 diesel ahead of the new regulations, which boosted our image from the political and environmental standpoints, and brought with it economic gains. The future looks very bright for us."